Sidemovement correcting members of a machine for correcting the sidemovement of a travelling sheet-like article are generally disposed at the selvedge of a travelling sheet-like article, respectively. When a travelling sheet-like article is displaced to exhibit a sidemovement, these correcting members work to move the selvedges of the travelling sheet-like article to predetermined directions, thereby to correct the travelling to a correct line.
As means for actuating the correcting member of the type above-mentioned, there is conventionally known, for example, an actuator comprising a screw shaft, nut means threadedly connected to the screw shaft, and an electric motor for reversively rotating either the screw shaft or the nut means. The correcting member which is connected to the nut means, is adapted to be moved together with the nut means in a predetermined direction by the reversible rotation of the motor.
The inventor has previously proposed apparatus for actuating a sidemovement correcting member of a machine for correcting the sidemovement of a travelling sheet-like article with the object of making the apparatus in compact design and improving the maneuverability of the apparatus.
As shown in FIG. 7, the apparatus previously proposed by the inventor comprises a reversible motor 1 having a hollow rotary shaft 2, bearings 3 for the shaft 2, a rotor 4 secured to the shaft 2 at its outer periphery, a stator 5 on the outer periphery of the rotor 4 and a casing 6 for housing the members above-mentioned, a screw shaft 7 of a predetermined length and a member 8 put on the screw shaft 7. The member 8 is secured to one end of the hollow rotary shaft 2 with a screw 9, and forms a nut means 11 provided with a circulating passage 10 for a plurality of lubricating balls 12. The screw shaft 7 is inserted into the member 8 and is threadedly connected thereto through the lubricating balls 12. The both ends of the screw shaft 7 is non-rotatably secured to supports 13.
With such arrangement, the forward and reverse rotations of the rotor 4 enable the motor 1 to be reciprocated axially of the screw shaft 7. When a sidemovement correcting member 15 of a machine for correcting the sidemovement of a travelling sheet-like article is secured to a pivot shaft 16a of a mounting member 16 pivotally connected to the top of the casing 6 through bearings 14, the apparatus can be utilized as means for reciprocating the correcting member 15 axially of the screw shaft 7. Since this apparatus is constructed so that the motor 1 itself is reciprocated, the entire arrangement is remarkably simplified as compared with a conventional apparatus requiring transmission means ( not shown ) such as belts, pulleys, an external motor. Thus, the entire apparatus can be advantageously forced in contact design. However, the use of a rotary motor as the motor 1 presents the following problems.
The ON and OFF operations of the motor 1 are made, for example, by a signal of detecting the sidemovement of a travelling sheet-like article and a signal of detecting the sidemovement correction, supplied from a detector (not shown) of a sidemovement correcting machine. However, a time delay often occurs between the ON/OFF operation of the motor 1 and the movement/stop of the correcting member 15. In particular, at the time the correcting member 15 is to stop, highly accurate control cannot be expected. In other words, excessive correction is made to a sheet-like article which is travelling in a zigzag line. This leads to the occurrence of another sidemovement of the travelling sheet-like article, or unnecessary movement of the correcting member 15. Moreover, noise due to the rotation of the motor produces another problem.